1. Field of the Invention
The .beta.-adrenergic blocking agents are pharmacologically active drugs which block the .beta.-adrenergic receptors. Propranolol, the best known member of the class is used to suppress arrhythmia, as well as in the treatment of hypertension. Other .beta.-adrenergic blocking agents which have been studied are dichloroisoproterenol, pronethalol, sotalol, oxprenolol, practolol, and butoxamine.
When these drugs are administered to a patient, it is important to determine the relation between administered dose and in vivo concentration for proper therapeutic response. In order to determine the level of the drug in the blood or other physiological fluid, sensitive tests which distinguish the drug from its metabolites and other concurrently administered drugs are necessary.
Competitive protein binding assays can be used for such determination. For these assays, there is a need for antibodies which are produced at high concentrations, bind to the drug, and only weakly bind to related drugs and metabolites which may be present. These antibodies are prepared using antigenic conjugates of derivatives of the drugs of interest.
Additionally, such assays require a reagent which produces a measurable, reproducible signal in relation to the concentration of drug in the assay medium. This reagent must effectively compete with the drug of interest for antibody binding, and should provide an easily measurable change in signal with small changes of the drug concentration over the concentration range of interest, 10-400 ng/ml in the case of propranolol. Additionally, the reagent should remain stable under assay conditions, and should have a good storage life.
2. Brief Description of the Prior Art
Descriptions of competitive protein binding assays may be found in U.S. Pat. Nos. 3,817,837, 3,850,752, 3,690,834, and in an article by Murphy, 27 J. Clin. Endocr. 973(1967). U.S. Pat. No. 3,875,011 discloses glucose-6-phosphate dehydrogenase conjugates for use in homogeneous enzyme immunoassays.
Preparation of antigenic conjugates and antibodies for a number of different drugs may be found in U.S. Pat. Nos. 3,888,866, 3,766,162, 3,843,696 and 3,878,187, and preparation of certain antigenic conjugates of propranolol derivatives for use in a radioimmunoassay is described in an article by Specter, et al. 196 J. Pharmacol. Exp. Ther. 517-523(1976). See also U.S. Pat. No. 4,070,492, which describes propranolol derivatives substituted at oxygen for the production of assay reagents.